Aero boost - gas turbine energy supplementing systems and efficient inlet cooling and heating, and methods of making and using the same

ABSTRACT

The invention relates generally to electrical power systems, including generating capacity of a gas turbine, and more specifically to pressurized air injection that is useful for providing additional electrical power during periods of peak electrical power demand from a gas turbine system power plant, as well as to inlet heating to allow increased engine turn down during periods of reduced electrical demand.

FIELD OF THE INVENTION

The invention relates generally to electrical power systems, includinggenerating capacity of a gas turbine, and more specifically topressurized air injection that is useful for providing additionalelectrical power during periods of peak electrical power demand from agas turbine system power plant, as well as to inlet heating to allowincreased engine turn down during periods of reduced electrical demand.

BACKGROUND OF THE INVENTION

Currently marginal energy is produced mainly by gas turbine, either insimple cycle or combined cycle configurations. As a result of loaddemand profile, the gas turbine base systems are cycled up duringperiods of high demand and cycled down or turned off during periods oflow demand. This cycling is typically driven by the Grid operator undera program called active grid control, or AGC. Also, in many electricalmarkets, peak power demands occur when it is hottest outside. Gasturbines naturally loose power and efficiency at elevated ambienttemperatures which further increases the number of gas turbines thatmust be run during peak periods. Unfortunately, because industrial gasturbines, which represent the majority of installed base, were designedprimarily for base load operation, when they are cycled, a severepenalty is associated with the maintenance cost of that particular unit.For example, a gas turbine that is running base load could go through anormal maintenance once every three years, or 24,000 hours at a cost inthe 2-3 million U.S. dollar range. That same cost could be incurred inone year for a plant that is forced to start up and shut down every day.

Currently these gas turbine plants can turn down to approximately 50% oftheir rated capacity. They do this by closing the inlet guide vanes ofthe compressor, which reduces the air flow to the gas turbine, alsodriving down fuel flow as a constant fuel air ratio is desired in thecombustion process. Maintaining safe compressor operation, andcompliance with emissions requirements, typically limit the level ofturn down that can be practically achieved.

The safe compressor lower operating limit is improved in current gasturbines by introducing warm air to the inlet of the gas turbine,typically from a mid stage bleed extraction from the compressor.Sometimes, this warm air is also introduced into the inlet to preventicing. In either case, when this is done, the work that is done to theair by the compressor is sacrificed in the process for the benefit ofbeing able to operate the compressor safely to a lower flow, thusincreasing the turn down capability and preventing icing of the inlet.This has a further negative impact on the efficiency of the system asthe work performed on the air that is bled off is lost. Additionally,the combustion system also presents a limit to the system.

The combustion system usually limits the amount that the system can beturned down because as less fuel is added, the flame temperaturereduces, increasing the amount of carbon monoxide (CO) emissions thatare produced. The relationship between flame temperature and COemissions is exponential with reducing temperature, consequently, as thegas turbine system gets near the flame temperature limit, the COemissions spike up, so a healthy margin is kept from this limit. Thischaracteristic limits all gas turbine systems to approximately 50% turndown capability, or, for a 100 MW gas turbine, the minimum power, ormaximum turn down, that can be achieved is about 50%, or 50 MW. As thegas turbine mass flow is turned down, the compressor and turbineefficiencies fall off as well, causing an increase in heat rate of thegas turbine. Some operators are faced with this situation every day andas a result, as the load demand falls, their gas turbine plants hittheir lower operating limit and they have to turn the gas turbines off,which costs them a tremendous maintenance cost penalty.

Another characteristic of a typical gas turbine is that as the ambienttemperature increases, the power output from the gas turbine system goesdown proportionately due to the linear effect of the reduced density asthe temperature of air increases. Power output can be down by more than10% from nameplate output during hot days, typically when peaking gasturbines are called on most to deliver power.

Another characteristic of typical gas turbines is that air that iscompressed and heated in the compressor section of the gas turbine isducted to different portions of the gas turbine's turbine section whereit is used to cool various components. This air is typically calledturbine cooling and leakage air (hereinafter “TCLA”), a term that iswell known in the art with respect to gas turbines. Although heated fromthe compression process, TCLA air is still significantly cooler than theturbine temperatures, and thus is effective in cooling those componentsin the turbine downstream of the compressor. Typically 10% to 15% of theair that comes in the inlet of the compressor bypasses the combustor andis used for this process. Thus, TCLA is a significant penalty to theperformance of the gas turbine system.

Another characteristic of many large frame engines used to generatepower is that the RPM is fixed because the shaftline of the gas turbineis fixed to the generator and the generator must spin at a specificspeed to generate electricity at a specific frequency, for example 3600RPM for 60 HZ and 3000 RPM for 50 HZ. The term “shaftline” means theshaft of the gas turbine and the shaft of the generator and includingany fixed ratio gearbox attached between those shafts, so that at alloperating conditions the ratio of revolutions per minute (RPM) of thegas turbine shaft to the RPM of the generator shaft remains constant. Ingas turbines that have free turbines or multiple turbine shafts within,this is not true. Consequently only one shaft of a multi-shaft gasturbine, the one tied to, or on the shaftline with, the generator, hasto spin at a constant rpm. This is a significant consideration wheninjecting air upstream of the combustor.

On a multi-shaft engine, like the LM6000 for example, when the air isinjected upstream of the combustor, the high pressure turbine actuallyspeeds up which drives the high pressure compressor harder, which inturn induces more air flow through the gas turbine's low pressurecompressor, and the compressor as a whole. Therefore, the increasedairflow that is being injected upstream of the combustor is the injectedair plus the additional flow that is induced in the gas turbine engine'score. Since the low pressure compressor is tied to the low pressureturbine (LPT) and generator, it spins at 3600 RPM (for a 60 HZgenerator) and additional air flow goes through the LPT because of thereduced pressure between the high pressure compressor (HPC) and LPC. Inother words, since the high pressure compressor is working harder andinducing flow through the low pressure compressor, the low pressurecompressor does not need to work as hard to compress the air going tothe combustor, so more of the energy that drives the low pressureturbine and the power turbine is available to drive the generator (orother load).

SUMMARY OF THE INVENTION

The present invention relates to improved electrical power systems andmethods of using the same, including increasing the capacity of a gasturbine.

The current invention, which may be referred to herein as TurboPHASE™,provides several options, depending on specific plant needs, to improvethe efficiency and power output of power plants using multi-shaft gasturbine engines, at low loads, and to reduce the lower limit of poweroutput capability of such gas turbines while at the same time increasingthe upper limit of the power output of the gas turbine, thus increasingthe capacity and regulation capability of a new or existing gas turbinesystem.

One aspect of the present invention relates to methods and systems thatallow running multi-shaft gas turbine systems to provide additionalpower quickly during periods of peak demand.

Yet another aspect of the present invention relates to methods andsystems that allow gas turbine systems to be more efficiently turneddown during periods of lowered demand.

One embodiment of the invention relates to a system comprising at leastone existing gas turbine that comprises a low pressure compressor, ahigh pressure compressor, a combustor, a high pressure turbine, and alow pressure turbine, wherein a first shaft connects the low pressurecompressor and the low pressure turbine, and a second shaft connects thehigh pressure compressor and the high pressure turbine, and furthercomprising an auxiliary compressor which is not the same as the lowpressure compressor or the high pressure compressor.

An advantage of preferred embodiments of the present invention is theability to efficiently increase the turn down capability of the gasturbine system during periods of lower demand and improve the efficiencyand output of the gas turbine system during periods of high demand.

Another advantage of additional preferred embodiments of the presentinvention is the ability to efficiently increase the turn downcapability of the gas turbine system during periods of low demand byusing an auxiliary compressor driven by a fueled engine, the operationof which is independent of the electric grid.

Another advantage of other preferred embodiments of the presentinvention is the ability to increase the turn down capability of the gasturbine system during periods of low demand by using an auxiliarycompressor driven by a fueled engine which produces heat that can beadded to compressed air flowing to the gas turbine, from the auxiliarycompressor.

Another advantage of additional preferred embodiments of the presentinvention is the ability to increase output of the gas turbine systemduring periods of high demand by using an auxiliary compressor which isnot driven by power produced by the gas turbine system.

Another advantage of the present invention is the ability to incorporateselective portions of the embodiments described herein on existing gasturbines to achieve specific plant objectives.

Another advantage of another embodiment of the present invention is thatbecause the incremental amount of compressed air can be added at arelatively constant rate over a wide range of ambient temperatures, thepower increase achieved by the gas turbine is also relatively constantover a wide range of ambient temperatures.

Other advantages, features and characteristics of the present invention,as well as the methods of operation and the functions of the relatedelements of the structure and the combination of parts will become moreapparent upon consideration of the following detailed description andappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic drawing of a first embodiment of the presentinvention including injection of compressed air from the booster systeminto the combustor of a multi-shaft gas turbine engine with inlet bleedheating.

FIG. 2 is a schematic drawing of an additional embodiment of the presentinvention showing injection of compressed air from the booster systeminto an inlet of the low pressure compressor of a multi-shaft gasturbine engine to provide inlet heating.

FIG. 3 is a schematic drawing of yet another alternate embodiment of thepresent invention showing injection of a first portion of compressed airfrom the booster system into an inlet of the high pressure compressor ofa multi-shaft gas turbine engine, and injection of a second portion ofcompressed air from the booster system into the combustor of themulti-shaft gas turbine engine.

FIG. 4 is a chart showing various locations of reference points, orstations, in a typical multi-shaft gas turbine engine.

DETAILED DESCRIPTION OF THE PRESENT EMBODIMENT

One aspect of the invention relates to a method of supplementing thepower output of a gas turbine system having in series a low pressurecompressor, a high pressure compressor, a combustor, a high pressureturbine, and a low pressure turbine, wherein a first shaft connects thelow pressure compressor and the low pressure turbine, and a second shaftconnects the high pressure compressor and the high pressure turbine, themethod comprising:

(i) providing a booster system having a fueled engine, and an auxiliarycompressor;

(ii) operating the fueled engine to drive the auxiliary compressor toproduce compressed air from the auxiliary compressor and hot exhaust gasfrom the fueled engine;

(iii) heating the compressed air with heat extracted from the hotexhaust gas, thereby producing hot compressed air; and

(iv) injecting the hot compressed air into the gas turbine systemdownstream of the high pressure compressor of the gas turbine system,thereby increasing the mass flow of air therethrough and augmenting thepower output of the gas turbine system.

According to one embodiment, the auxiliary compressor is a multistagecompressor having at least one upstream compression stage and at leastone downstream compression stage fluidly downstream of the upstreamcompression stage, and the step of operating the fueled engine to drivethe auxiliary compressor to produce compressed air from the auxiliarycompressor includes the step of cooling the compressed air exiting theupstream compression stage before delivering it to the downstreamcompression stage. Preferably, the step of injecting the hot compressedair into the gas turbine system downstream of the compressor of the gasturbine system includes injecting the hot compressed air into thecombustor.

According to another embodiment, the step of injecting the hotcompressed air into the gas turbine system downstream of the compressorof the gas turbine system includes injecting the hot compressed air intothe combustor.

Another aspect of the invention relates to a method of supplementing thepower output of a gas turbine system having in series a low pressurecompressor, a high pressure compressor, a combustor, a high pressureturbine, and a low pressure turbine, wherein a first shaft connects thelow pressure compressor and the low pressure turbine, and a second shaftconnects the high pressure compressor and the high pressure turbine, themethod comprising:

(i) providing a booster system having a fueled engine, and an auxiliarycompressor;

(ii) operating the fueled engine to drive the auxiliary compressor toproduce compressed air from the auxiliary compressor;

(iii) injecting a first portion of the compressed air into an inlet ofthe high pressure compressor of the gas turbine system downstream of thelow pressure compressor.

According to one embodiment, the the step of injecting the first portionof the compressed air into an inlet of the high pressure compressor ofthe gas turbine system downstream of the low pressure compressor ispreceded by the step of cooling the first portion of compressed air.Preferably, the step of operating the fueled engine to drive theauxiliary compressor to produce compressed air from the auxiliarycompressor includes the step of producing hot exhaust gas from thefueled engine.

According to preferred embodiments, the step of producing hot exhaustgas from the fueled engine is followed by the step of heating a secondportion of the compressed air with heat extracted from the hot exhaustgas, thereby producing hot compressed air. According to still furtherpreferred embodiments, the method comprises the step of injecting thefirst portion of the compressed air into an inlet of the high pressurecompressor of the gas turbine system downstream of the low pressurecompressor and the step of injecting the hot compressed air into the gasturbine system downstream of the high pressure compressor. Preferably,the step of injecting the hot compressed air into the gas turbine systemdownstream of the high pressure compressor of the gas turbine systemincludes injecting the hot compressed air into the combustor.

Yet another aspect of the invention relates to an apparatus forsupplementing the power output of a gas turbine system having in seriesa low pressure compressor, a high pressure compressor, a combustor, ahigh pressure turbine, and a low pressure turbine, wherein a first shaftconnects the low pressure compressor and the low pressure turbine, and asecond shaft connects the high pressure compressor and the high pressureturbine, the apparatus comprising:

(i) an auxiliary compressor to produce compressed air, the auxiliarycompressor having at least one compressed air outlet;

(ii) a fueled engine connected to the auxiliary compressor to drive theauxiliary compressor, the fueled engine producing hot exhaust gas andhaving an exhaust outlet; and

(iii) a recuperator having a first recuperator inlet, a secondrecuperator inlet, a first recuperator outlet, and a second recuperatoroutlet, the first recuperator inlet fluidly connected to the at leastone compressed air outlet, the second recuperator inlet fluidlyconnected to the exhaust outlet, the first recuperator outlet fluidlyconnected to the first recuperator inlet and fluidly connected to thegas turbine system downstream of the high pressure compressor of the gasturbine system, and the second recuperator outlet is fluidly connectedto the second recuperator inlet;

wherein heat from the hot exhaust gas is transferred to the compressedair in the recuperator prior to being injected into the gas turbinesystem.

According to one embodiment, the auxiliary compressor is a multistagecompressor, and each stage of the multistage compressor has a stageinlet and a stage outlet. Preferably, the apparatus further comprises anintercooler heat exchanger fluidly connected to at least one of thestage inlets and at least one of the stage outlets to cool thecompressed air exiting the at least one of the stage outlets prior todelivering the compressed air to the at least one of the stage inletsdownstream thereof. According to one preferred embodiment, the firstrecuperator outlet is fluidly connected to the combustor of the gasturbine system.

Yet another aspect of the invention relates to an apparatus forproviding inlet heating on a gas turbine system having in series a lowpressure compressor, a high pressure compressor, a combustor, a highpressure turbine, and a low pressure turbine, wherein a first shaftconnects the low pressure compressor and the low pressure turbine, and asecond shaft connects the high pressure compressor and the high pressureturbine, the apparatus comprising:

-   -   (i) an auxiliary compressor to produce compressed air, the        auxiliary compressor having at least one compressed air outlet;    -   (ii) a fueled engine connected to the auxiliary compressor to        drive the auxiliary compressor, the fueled engine producing hot        exhaust gas and having an exhaust outlet; and    -   (iii) a recuperator having a first recuperator inlet, a second        recuperator inlet, a first recuperator outlet, and a second        recuperator outlet, the first recuperator inlet fluidly        connected to the at least one compressed air outlet, the second        recuperator inlet fluidly connected to the exhaust outlet, the        first recuperator outlet fluidly connected to the first        recuperator inlet and fluidly connected to an inlet of the low        pressure compressor, and the second recuperator outlet is        fluidly connected to the second recuperator inlet;    -   wherein heat from the hot exhaust gas is transferred to the        compressed air in the recuperator prior to being injected into        the gas turbine system.

Yet another aspect of the invention relates to an apparatus forsupplementing the power output of a gas turbine system having in seriesa low pressure compressor, a high pressure compressor, a combustor, ahigh pressure turbine, and a low pressure turbine, wherein a first shaftconnects the low pressure compressor and the low pressure turbine, and asecond shaft connects the high pressure compressor and the high pressureturbine, the apparatus comprising:

(i) an auxiliary compressor to produce compressed air, the auxiliarycompressor having at least one compression stage and at least one outletof the compression stage;

(ii) a fueled engine connected to the auxiliary compressor to drive theauxiliary compressor, the fueled engine producing hot exhaust gas andhaving an exhaust outlet; and

(iii) a cooling tower having at least one inlet and at least one outlet,the at least one inlet of the cooling tower fluidly connected to the atleast one outlet of the compression stage, and the at least one outletof the cooling tower fluidly connected to an inlet of the high pressurecompressor downstream of the low pressure compressor.

A still further aspect of the invention relates to an apparatus forsupplementing the power output of a gas turbine system having in seriesa low pressure compressor, a high pressure compressor, a combustor, ahigh pressure turbine, and a low pressure turbine, wherein a first shaftconnects the low pressure compressor and the low pressure turbine, and asecond shaft connects the high pressure compressor and the high pressureturbine, the apparatus comprising:

(i) an auxiliary compressor to produce compressed air, wherein theauxiliary compressor is a multistage compressor, and each stage of themultistage compressor has a stage inlet and a stage outlet;

(ii) a fueled engine connected to the auxiliary compressor to drive theauxiliary compressor, the fueled engine producing hot exhaust gas andhaving an exhaust outlet;

(iii) a cooling tower having a first inlet, a first outlet, and a secondoutlet, the first inlet of the cooling tower fluidly connected to one ofthe stage outlets, the first outlet of the cooling tower fluidlyconnected to one of the stage inlets, and the second outlet of thecooling tower fluidly connected to an inlet of the high pressurecompressor downstream of the low pressure compressor; and

(iv) a recuperator having a first recuperator inlet, a secondrecuperator inlet, a first recuperator outlet, and a second recuperatoroutlet, the first recuperator inlet fluidly connected to one of thestage outlets, the second recuperator inlet fluidly connected to theexhaust outlet, the first recuperator outlet fluidly connected to thefirst recuperator inlet and fluidly connected to an inlet of the gasturbine system downstream of the high pressure compressor, and thesecond recuperator outlet is fluidly connected to the second recuperatorinlet;

wherein heat from the hot exhaust gas is transferred to the compressedair in the recuperator prior to being injected into the gas turbinesystem.

Preferably, the first recuperator outlet is fluidly connected to thecombustor of the gas turbine system.

Yet another aspect of the invention relates to a method of providinginlet heating on a gas turbine system having in series a low pressurecompressor, a high pressure compressor, a combustor, a high pressureturbine, and a low pressure turbine, wherein a first shaft connects thelow pressure compressor and the low pressure turbine, and a second shaftconnects the high pressure compressor and the high pressure turbine, themethod comprising:

(i) providing a booster system having a fueled engine, and an auxiliarycompressor;

(ii) operating the fueled engine to drive the auxiliary compressor toproduce compressed air from the auxiliary compressor and hot exhaust gasfrom the fueled engine;

(iii) heating the compressed air with heat extracted from the hotexhaust gas, thereby producing hot compressed air; and

(iv) injecting the hot compressed air into an inlet of the low pressurecompressor of the gas turbine system.

FIG. 1 shows the layout for an air injection system of the presentinvention, referred to as “TurboPHASE”, into a multi-shaft gas turbine,where the air injection system includes a recuperator 110, an auxiliarycompressor 400, and a fueled engine 101 (along with a cooling tower 107that cools the air being compressed by the auxiliary compressor 400). Asused herein, the term “fueled engine” means a heat engine, such as apiston driven or rotary (e.g. Wankel) internal combustion engine (e.g.gasoline engine, diesel engine, natural gas fired engine, or similarfuels, or a combination of such fuels) or a gas turbine, that produceswork by combusting a fuel with air to heat a working fluid which thendrives blades or the like. The low pressure compressor 10 (referred toherein as “LPC”) is connected to the low pressure turbine 14 (referredto herein as “LPT”) and the power turbine 15 (referred to herein as“PT”) which is also connected to the load or generator 16. The highpressure compressor 11 (referred to herein as “HPC”) is connected to thehigh pressure turbine 13 (referred to herein as “HPT”). The HPC 11, theHPT 13, and the shaft 19 that connects them are commonly known as the“HP Core”, and the balance is known as the “LP Section”. The HP Core andthe LP Section are fluidly connected both in the compression section(the LPC and the HPC) and in the turbine section (the HPT, LPT and PT).The combustor 12 takes the HPC pressurized air flowing from the HPC exit17 and adds energy to the pressurized air by burning fuel in it and thenreturning the pressurized air to the inlet 18 of the HPT. The HP Coreshaft 19 is hollow to allow the two shafts to rotate relative to eachother.

The balance of the diagram in FIG. 1, items 100 to 111 inclusive,produce hot, compressed air through recuperator exit 112 to be injectedinto the combustor 12 in addition to the pressurized air that the gasturbine is delivering through the HPC exit 17. This hot compressed airdelivered through recuperator exit 112 is generated by an auxiliarycompressor 400 that is intercooled, and preferably driven by areciprocating fueled engine 101. As shown in FIG. 1, ambient air entersthe fueled engine 101 at the fueled engine intake 100, and ambient airenters auxiliary compressor 400 at the compressor inlet 111. The fueledengine 101 mechanically drives the shaft 103 of the auxiliary compressor400. Typically there is a coupling—hydraulic, mechanical, ormechanical/hydraulic—(not shown) connected to a gearbox between thefueled engine 101 and the auxiliary compressor 400 to increase the speedof the auxiliary compressor 400 to the correct compressor inlet RPM. Thecoupling and the gearbox are not shown in FIG. 1 for simplicity, but asthose skilled in the art will readily appreciate, would likely beincluded in most applications.

As the input shaft 103 is turned, several stages of the auxiliarycompressor 400 are turned (or driven). FIG. 1 shows an exemplarytwo-stage auxiliary compressor 400, however, more stages may beapplicable as pressure requirements vary depending on gas turbinecombustor pressures. Regardless of the actual number of stages, eachstage of the multistage compressor has a stage inlet (e.g. 108) and astage outlet (e.g. 106). The air enters the first stage 104 of themulti-stage auxiliary compressor 400 through air inlet 111 and exitsthrough first stage exit 106 at a higher pressure and subsequently ahigher temperature than when it entered the first stage 104. Thishotter, higher pressure compressed air then enters the intercooler, inFIG. 1 shown as a cooling tower 107, and is cooled to approximately 100Fahrenheit (° F.). The cooling tower 107 may be a completely separatesystem, or a part of the existing plant cooling system. After thecompressed air is cooled, the compressed air exits the cooling tower 107through cooling tower exit and enters the inlet 108 of the second stageof the auxiliary compressor 105 where it is further compressed. As thoseskilled in the art will readily appreciate, the first stage 104 of themulti-stage auxiliary compressor 400 is upstream of the second stage 105of the multi-stage auxiliary compressor 400, which is downstream of thefirst stage 104. Although only two stages of the auxiliary compressor400 are shown in FIGS. 1-3 for clarity, it is to be understood that ifthere are additional stages in the auxiliary compressor 400, thiscompression and intercooling process is repeated for each stage of themultistage auxiliary compressor 400 until the desired pressure isachieved. Then the compressed air exits the auxiliary compressor 400after the last stage of compression through the auxiliary compressorexit 109, which is connected to the inlet of the first heat transfercircuit of the recuperator 110, and enters the first heat transfercircuit of the recuperator 110. In the recuperator 110, the warmcompressed air is further heated using the exhaust of the fueled engine101 which is fed into the second heat transfer circuit of therecuperator 110 through the fueled engine exhaust path 102. The fueledengine exhaust path 102 is connected to the inlet of the second heattransfer circuit of the recuperator 110, so that the exhaust of thefueled engine flows through the second heat transfer circuit of therecuperator 110, and then exits the second heat transfer circuit of therecuperator 110 and exhausts to the atmosphere, having been cooled as aresult of transferring heat to the compressed air in the first heattransfer circuit of the recuperator 110. The compressed air in the firstheat transfer circuit, heated in the recuperator 110 as the result ofthe transfer of heat from the exhaust in the second circuit of therecuperator 110, exits the first heat transfer circuit of the therecuperator 110 through recuperator exit 112 and flows into an inlet ofthe combustor 12 upstream of the combustor 12 where it is added to thepressurized air flowing from the exit 17 of the HPC of the gas turbineand is entering the combustor 12 from the main compressor exit 17.

When the hot compressed air from the first heat exchange circuit of therecuperator 110 is added to the combustor 12, more fuel is added to thecombustor 12 through fuel line 22 to maintain the same firingtemperature as before the hot compressed air from the first heatexchange circuit of the recuperator 110 was added. As those skilled inthe art will readily appreciate, the additional compressed air and fueladded to the combustor 12 provides more energy to the inlet 18 of theHPT 13, and consequently, more power is produced by the gas turbine HPT13 which in turn spins the HP Core shaft 19 faster. This in turn inducesand compresses more flow through the HPC 11, since all of the additionalenergy extracted by the HPT 13 is used as work in the HPC 11 becausethere is no external load or generator 16 attached to the HP Core shaft19. Although the additional compressed air added to the combustor 12from the first heat exchange circuit of the recuperator 110, and theadditional fuel that is added to the combustor 12 to maintain the firingtemperature, increases the RPM of the HP Core shaft 19, the LPC 10 stillspins at the same RPM, since its speed is fixed by the generator, butthe variable guide vanes in the LPC 10 can be adjusted to allow the LPC10 to pass more flow.

Tables 1 and 2 below shows results from a commercial software programcalled “GasTurb”. In using GasTurb for analysis of the presentinvention, injection into the combustor 12 of compressed air from thefirst heat exchange circuit of the recuperator 110 is simulated byadding a negative bleed number for the HPC 11. The stationidentifications listed in Tables 1 and 2 are shown in FIG. 4. (Note: theterm “TurboPHASE” as used in these tables refers to the presentinvention, the elements of which are identified in FIG. 1 by referencethe numerals 100-112.)

TABLE 1 GasTurb program results for 14.4 lbs/sec injection into anLM6000 Design Hot Day Hot Day w/TurboPHASE TurboPHASE Flow (lb/s) — —14.4 14.4 TurboPHASE Location — — HPC Exit Booster Exit Power (MW) 51.8143.45 51.12 44.16 Heat Rate BTU/(kWh) 8529 8953 8156 8854 Mass Flow(ls/s) 306 270 296 273

TABLE 2 GasTurb program results for 14.4 lbs/sec injection into anLM6000 Hot Day HPC Exit TurboPHASE Hot Day Booster Exit Design Hot Day14.4 lb/s TurboPHASE 14.4 lb/s Station W (lb/s) T (R) P (psia) W (lb/s)T (R) P (psia) W (lb/s) T (R) P (psia) W (lb/s) T (R) P (psia) amb 51914.7 555 14.7 555 14.7 0 554.67 14.696 1 300.3 519 14.7 265.5 555 14.7275.9 555 14.7 254.2 555 14.7 2 300.3 519 14.7 265.5 555 14.7 275.9 55514.7 254.2 555 14.7 24 300.3 696 36.7 265.5 743 36.4 275.9 731 34.7254.2 754 37.7 25 300.3 696 36.0 265.5 743 35.8 275.9 731 34.1 268.5 75437.2 3 297.3 1517 458.0 262.8 1549 406.6 273.2 1598 449.1 265.8 1559411.1 31 243.3 1517 458.0 215.1 1549 406.6 237.9 1598 449.1 217.5 1559411.1 4 248.9 3050 444.2 220.0 3050 394.2 243.2 3050 434.9 222.5 3050398.5 41 272.9 2928 444.2 241.3 2931 394.2 265.3 2940 434.9 243.9 2931398.5 43 272.9 2183 103.5 241.3 2196 92.8 265.3 2192 101.0 243.9 219793.8 44 303.0 2121 103.5 267.8 2137 92.8 292.9 2140 101.0 270.8 213993.8 45 303.0 2121 102.5 267.8 2137 91.8 292.9 2140 100.0 270.8 213992.8 49 303.0 1393 14.8 267.8 1439 14.8 292.9 1417 14.8 270.8 1437 14.85 306.0 1391 14.8 270.5 1437 14.8 295.7 1416 14.8 273.5 1436 14.8 6306.0 1391 14.7 270.5 1437 14.7 295.7 1416 14.7 273.5 1436 14.7

As shown in Table 1, the power output of the gas turbine increases from43.45 MW on a 95° F. (approximately 555 degrees Rankine, as shown inTable 2) day to 51.12 MW, an increase of 7.67 MW or 18% with aninjection rate of 14.4 lbs/sec or 5.5% of the baseline hot day LPC inletflow (station 1, 265.5 lbs/sec). Also notice in Tables 1 and 2 that theexhaust flow from the gas turbine has increased from 270 to 295.7lbs/sec (rounded to 296), or 9.3%. The extra 3.8% is “induced” flowgenerated by the gas turbine HPC 11. This is significant as the cost ofthe TurboPHASE system (100-112 in FIG. 1) is primarily tied to the massflow rate the system can deliver, and consequently, the effective costfrom a “power delivered” standpoint, or $/kW, is improved on a gasturbine that has multiple shafts 19, 20 as compared to a single, or“fixed”, shaft machine. On an F-class fixed shaft engine, such as the GEframe 7FA gas turbine engine, a TurboPHASE system adding 14.4 lbs/sec ofair to the combustor could produce 5.1 additional megawatts. However,because of the induced flow and additional power it creates in amultiple shaft engine, the multiple shaft engine has an effectiveimprovement in output of 50% with very little cost increase. Forexample, the HP Core shaft 19 speed increases by approximately 1000 RPMas compared to baseline hot day RPM, and only 600 RPM compared tostandard day RPM.

FIG. 2 shows an alternate embodiment of the present invention of FIG. 1,except that the cooling tower is omitted in this embodiment, andcompressed air discharged from the exit 206 of the first stage 104 ofthe auxiliary compressor 400 is routed to the inlet of the first heatexchange circuit of the recuperator 110 instead of to the cooling tower,and the downstream stages, such as 105, are either mechanically oraerodynamically disconnected from the shaft 103 of the auxiliarycompressor 400. If the downstream stages are mechanically disconnected,those stages will have zero RPM. On the other hand, if the downstreamstages of the auxiliary compressor 400 are aerodynamically disconnected,those stages will maintain speed while being aerodynamically unloaded,and any air that is flowing through those stages will be discharged tothe atmosphere 207. In either case, only the first stage 104 isproducing the compressed air that enters the recuperator 110 and getsheated therein, so minimal energy is used to produce the compressed airthat enters the first heat exchange circuit of the recuperator 110. Thehot compressed air exiting the first heat exchange circuit discharge 212of the recuperator 110 enters the inlet of the gas turbine andeffectively produces inlet heating much more economically than occurswith typical gas turbine inlet heating systems.

Normally, in a gas turbine inlet heating system, air is taken, or“bled”, from the compressor discharge 17 at full pressure andtemperature. With preferred TurboPHASE systems, inlet heating isaccomplished with a fraction of the fuel consumption, producing asignificant efficiency benefit. This type of inlet heating can beaccomplished on a multi-shaft gas turbine or a single shaft gas turbine.A typical gas turbine can have as much as 6% inlet bleed and almost halfof the fuel entering the gas turbine is used by the gas turbinecompressor to pressurize and heat the air, therefore 3% of the fuelentering the gas turbine is effectively wasted just to heat the inletup, resulting in a 3% efficiency penalty. With the proposed system shownin FIG. 2, only ⅓ of the fuel would be required for the same mass flowof hot air, resulting in an efficiency penalty of approximately 1%,instead of 3%, for a savings of 2%.

FIG. 3 shows another alternate embodiment of FIG. 1, however, in FIG. 3,the first stage 304 of the auxiliary compressor 400 is sized to producesignificantly more flow than the downstream compressor stages, such as105. A first portion of the compressed air produced by the first stage304 of the auxiliary compressor is extracted through a discharge line301 after it is cooled in the cooling tower 107, and is injected intothe HPC 11 downstream of the LPC 10, (this location is referred to asthe “Booster Exit” in Tables 1 and 2, and is the location shown asstation 25 in FIG. 4). Effectively this produces an inlet chillingeffect on the HPC 11 which tends to slow the rpm of the HPT 13, acounterbalancing tool if the air injection system shown in FIG. 1produces HP Core shaft 19 speeds that are undesirably high. A secondportion of the compressed air that flows to the cooling tower 107 fromthe exit 306 of the first stage of the auxiliary compressor 400 iscooled and flows from an exit of the cooling tower 107 into the inlet108 of the second stage 105 of the auxiliary compressor 400, exits viaoutlet 109, is then heated in the recuperator 110, and injected into thegas turbine system downstream of the HPC 11, preferably in the combustor12.

Table 1 shows the results of 14.4 lbs/sec injection of compressed air,at approximately 283° F., at the Booster Exit. With injection of thecompressed air at this point, the RPM on the HP Core shaft 19 is reducedby approximately 300 RPM. When the temperature of the compressed airinjected at the Booster Exit is decreased by cooling in cooling tower107 to 100° F. to become cool compressed air, this mixes with the 283°F. air and reduces the temperature of the air entering the HPC 11. (Thiscooling effect is not shown in Table 1 or 2). Therefore, with theinjection of the cool compressed air (at approximately 100° F.) at theBooster Exit, the effective temperature of all of the air entering theinlet of the HPC 11 is reduced to 273° F., yielding 10° F. of inletcooling which will further decrease the rpm of the HP Core shaft 19while at the same time increasing the flow through the gas turbineengine by almost 2%.

As those skilled in the art will readily appreciate, the output of thegas turbine increases from the 0.71 MW improvement shown in Table 1(44.16 MW-43.45 MW on a hot day) to almost 1.0 MW just from theinjection of the 14.4 lbs/sec at the Booster Exit. On a combinedinjection system (i.e. one that injects 14.4 lbs/sec at the Booster Exitand injects 14.4 lbs/sec into the HPC exit 17 or combustor 12),injecting 14.4 lbs/sec of cool air into the Booster Exit and injecting14.4 lbs/sec of hot air into the HPC exit 17 or combustor 12 (or 5.5%injection into both locations), the HP Core shaft 19 rpm remains almostconstant while the gas turbine engine induces an additional 4.8% moreflow through the LPC 10. This combined injection system can be balancedto control the HP Core shaft 19 rpm if required while at the same timealmost doubling the flow that produces power in the turbine andgenerator (load). In this example, the first stage 304 of the multistagecompressor 400 is flowing 28.8 lbs/sec and half of the flow is taken offafter the cooling tower 107 and this cool compressed air is injected inthe Booster Exit and the other half continues through the latter stages105 of the multistage compressor 400 and is ultimately heated in therecuperator 110 and then the hot compressed air is injected into the HPCexit 17 area (i.e combustor 12 input area). The combined injectionsystem produces 7.67 MW from the injection of hot compressed air at theHPC exit 17 (or combustor 12 inlet) and 1.0 MW from the cold compressedair injected at the Booster Exit, for a total increase of 8.67 MW.

As those skilled in the art will readily appreciate, the mass flow ofthe first portion of compressed air flowing from the cooling tower 107through discharge line 301 injected at the Booster Exit may besubstantially different than the mass flow of the second portion ofcompressed air flowing from the first heat transfer circuit of therecuperator 110 at recuperator exit 112 and preferably injected into theinlet of the combustor 12. Depending on the particular application, itmay be desirable to inject most, if not all of the compressed airentering the cooling tower 107 from exit 306 of the first stage of theauxiliary compressor 400 into the inlet to the HPC 11 downstream of theLPC 10 (i.e. at the “Booster Exit”).

As those skilled in the art will readily appreciate, each of theembodiments of the present invention includes flow control valves,backflow prevention valves, and shut-off valves as required to insurethat the flow of air, compressed air, and exhaust flow only in thedirections shown in FIGS. 1-3. While the particular systems, components,methods, and devices described herein and described in detail are fullycapable of attaining the above-described objects and advantages of theinvention, it is to be understood that these are the presently preferredembodiments of the invention and are thus representative of the subjectmatter which is broadly contemplated by the present invention, that thescope of the present invention fully encompasses other embodiments whichmay become obvious to those skilled in the art, and that the scope ofthe present invention is accordingly to be limited by nothing other thanthe appended claims, in which reference to an element in the singularmeans “one or more” and not “one and only one”, unless otherwise sorecited in the claim. It will be appreciated that modifications andvariations of the invention are covered by the above teachings andwithin the purview of the appended claims without departing from thespirit and intended scope of the invention.

1. A method of efficiently operating a gas turbine energy system,comprising: (a) providing a multiple shaft gas turbine engine having inseries a low pressure compressor, a high pressure compressor, acombustor, a high pressure turbine, and a low pressure turbine, whereina first shaft connects the low pressure compressor and the low pressureturbine, and a second shaft connects the high pressure compressor andthe high pressure turbine; (b) providing a booster system having afueled engine, an auxiliary compressor, a cooling tower, and arecuperator; (c) pressurizing ambient air using the auxiliary compressordriven by the fueled engine to produce compressed air, whileintercooling the compressed air between compression stages bytransferring heat therefrom to the cooling tower; (d) heating thecompressed air in the recuperator using exhaust from the fueled engineand then injecting said compressed air into said combustor.
 2. A methodof efficiently operating a gas turbine energy system, comprising: (a)providing a multiple shaft gas turbine engine having in series a lowpressure compressor, a high pressure compressor, a combustor, a highpressure turbine, and a low pressure turbine, wherein a first shaftconnects the low pressure compressor and the low pressure turbine, and asecond shaft connects the high pressure compressor and the high pressureturbine; (b) providing a booster system having a fueled engine, anauxiliary compressor and a recuperator; (c) pressurizing ambient airusing the auxiliary compressor driven by the fueled engine to producecompressed air; (d) heating the compressed air in the recuperator usingexhaust from the fueled engine and then injecting said compressed air aninlet of said low pressure compressor.
 3. A method of efficientlyoperating a gas turbine energy system, comprising: (a) providing amultiple shaft gas turbine engine having in series a low pressurecompressor, a high pressure compressor, a combustor, a high pressureturbine, and a low pressure turbine, wherein a first shaft connects thelow pressure compressor and the low pressure turbine, and a second shaftconnects the high pressure compressor and the high pressure turbine; (b)providing a booster system having a fueled engine, an auxiliarycompressor, a cooling tower, and a recuperator; (c) pressurizing ambientair using the auxiliary compressor driven by the fueled engine toproduce compressed air, while intercooling the compressed air betweencompression stages by transferring heat therefrom to the cooling tower;(d) injecting a first portion of said compressed air into an inlet ofsaid high pressure compressor, and heating a second portion of saidcompressed air in the recuperator using exhaust from the fueled engineand then injecting said second portion of compressed air into saidcombustor.